Lennox SL280UHNVK Series Gas Furnace

Important Safety Information

General Warnings

⚠️ WARNING

This furnace is equipped with an ignition control factory enabled for use with Lennox A2L refrigerant systems. Disabling the refrigerant detection functionality on A2L system is prohibited by safety codes. Refer to furnace installation instructions for non-A2L and non-Lennox refrigerant system setup.

⚠️ WARNING

Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury or loss of life. Installation and service must be performed by a licensed professional HVAC installer or equivalent, service agency, or the gas supplier.

? WARNING FIRE OR EXPLOSION HAZARD.

Failure to follow safety warnings exactly could result in serious injury, death, or property damage.

Flammable Materials and Installation

⚠️

Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance.

⚠️

Installation and service must be performed by a qualified installer, service agency or the gas supplier.

What to Do If You Smell Gas

⚠️

• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any phone in your building.
• Leave the building immediately.
• Immediately call your gas supplier from a neighbor's phone. Follow the gas supplier's instructions.
• If you cannot reach your gas supplier, call the fire department.

Parts Identification

Figure 1: Furnace Components

Diagram showing a cutaway view of the SL280UHNVK gas furnace with the following components labeled: TOP CAP, COMBUSTION AIR INDUCER, GAS VALVE, ACCESS PANEL, HEAT EXCHANGER ASSEMBLY, BLOWER MOTOR, LOW GWP IGNITION CONTROL.

Figure 2: Control Panel Connections

Diagram of the two-stage, variable speed, communicating control panel with labeled interfaces and components: HUMIDIFIER INTERFACE, FLAME SENSOR INTERFACE, LOW GWP ALARM/ZONE INTERFACE, LOW GWP TEST PUSH BUTTON, AUXILIARY TEMPERATURE SENSOR CONNECTOR, LOW GWP SENSORS INTERFACE, DIP SWITCHES, LGWP SENSORS ENABLE/DIABLE DIP SWITCHES (S4), HEAT, COOL, ADJUST CFM, COOL OFF DELAY SELECTION, DIAGNOSTIC RECALL PUSH BUTTON, DIP SWITCH, CONSTANT TORQUE ECM MOTOR TAPS, OUTDOOR & DISCHARGE AIR TEMPERATURE SENSOR CONNECTOR, 120V POWER INTERFACE, ZONE ALARM INTERFACE, LINE, FMP, CIRC, HSE/CAI, NEUTRAL, CAI/HSI INTERFACE, ECM INDOOR BLOWER MOTOR INTERFACE, SEGMENT LED, MAIN HARNESS INTERFACE, FIELD CLIPABLE TRACES, W915 2 STAGE COMPR, W951 HEAT PUMP, W914 DEHUM/DS, RDH, DS, THERMOSTAT TERMINAL BLOCK, FACTORY POSITION-RS BUS CONNECTIONS.

Figure 3: Gas Valve

Diagram of the SIT Valve showing pressure and signal ports (Supply Pressure Post, Manifold Pressure Post, Air Signal Post) and control positions (VENT, RAD, PR, POUT, ADJ). The gas valve is shown in the OFF position.

Homeowner Information

Notice to Homeowner

ℹ️ Notice to Homeowner

This furnace is equipped with safety devices that protect you and your property. If one or more of these devices is activated, furnace operation will stop. If your home is left unattended for an extended period of time, equipment operation must be checked periodically.

Water Supply Recommendation

If it is not possible to check equipment operation when the home is unattended, the water supply to the house should be shut off and the pipes should be drained. This will prevent problems associated with a NO HEAT condition (frozen pipes, etc.).

Operation and Safety

General Precautions

⚠️ CAUTION

Before attempting to perform any service or maintenance, turn the electrical power to unit OFF at the disconnect switch.

ℹ️ NOTICE

Any additions, changes, or conversions required in order for the appliance to satisfactorily meet the application needs must be made by a licensed professional installer (or equivalent) using factory-specified and approved parts.

Safety Instructions

• Keep the furnace area clear and free of combustible material, gasoline, and other flammable vapors and liquids. If it is installed in an insulated area, the furnace must be kept free of insulating material. Insulating material may be combustible.
• DO NOT obstruct air flow to unit. Unit must receive an unobstructed flow of combustion and ventilating air. DO NOT block or obstruct air openings on the furnace or air openings to the area in which the furnace is installed. Take care to maintain established clearances surrounding the furnace.
• DO NOT store chlorine or fluorine products near unit or introduce these products into the combustion air. These products can cause furnace corrosion.
• DO NOT draw return air from a room where this furnace, or any other gas appliance (i.e., a water heater), is installed. When return air is drawn from a room, a negative pressure is created in the room. If a gas appliance is operating in a room with negative pressure, the flue products can be pulled back down the vent pipe and into the room. This reverse flow of the flue gas may result in incomplete combustion and the formation of carbon monoxide gas. This toxic gas might then be distributed throughout the house by the furnace duct system.

Blower Door Safety

⚠️ WARNING

The blower door must be securely in place when the blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into the living space resulting in personal injury or death.

Gas Appliance Safety

Your furnace is a gas appliance. It is critical that the gas supplied to the unit be completely burned to avoid the production of carbon monoxide gas. Complete combustion of the gas requires, but is not limited to, correct gas pressure and gas flow rate, adequate combustion air and proper venting.

Asphyxiation Hazard

⚠️ WARNING

The exhaust vent for this furnace must be leak-free and must be securely connected to the furnace flue collar at all times.

For your safety and to fulfill the terms of the limited warranty, a licensed professional service technician (or equivalent) must annually inspect this furnace and its vent system.

Exposure to carbon monoxide gas can cause personal injury and even death to all occupants, including pets. Any item that is powered by, or gives off heat from, a combustion process (including lawn mowers, automobiles, and fireplaces) has the potential to produce carbon monoxide gas. Because of this, Lennox recommends the use of a carbon monoxide detector in your home, even if you do not own gas appliances. Reliable detectors are available at reasonable retail prices. Contact your Lennox dealer for more details about this investment in your safety.

Your furnace is designed to meet standards set by national agencies, and to operate safely when properly installed and maintained. However, the unit's performance can be greatly impacted by the individual installation and the operating environment. It is your responsibility to ensure that this appliance is maintained.

Proper maintenance is critical for your safety and the satisfactory operation of the product. Lennox strongly recommends annual inspection and maintenance of this appliance. Contact your Lennox dealer for an inspection by a licensed professional service technician.

Start-Up & Operation

⚠️ WARNING

If you do not follow these instructions exactly, a fire or explosion may result causing property damage, personal injury or death.

BEFORE LIGHTING smell all around the appliance area for gas. Be sure to smell next to the floor because some gas is heavier than air and will settle on the floor.

The gas valve on the SL280UHNVK is equipped with a gas control switch. Use only your hand to move the gas control switch. Never use tools. If the switch will not move by hand, do not try to repair it. Call a licensed professional service technician (or equivalent). Force or attempted repair may result in a fire or explosion.

Operating the Gas Valve

Placing the SL280UHNVK Furnace into Operation

SL280UHNVK units are equipped with an ignition control. Do not attempt to manually light the burner on these furnaces. Each time the thermostat calls for heat, the burner will automatically light.

Operating the Gas Valve (Figure 3)

1. STOP! Read the safety information at the beginning of this section.
2. Set the thermostat to the lowest setting.
3. Turn off all electrical power to the unit.
4. This furnace is equipped with an ignition device which automatically lights the burners. Do not try to light the burners by hand.
5. Remove the access panel.
6. Move switch on gas valve to OFF. Do not force. See figure 3.
7. Wait five minutes to clear out any gas. If you then smell gas, STOP! Immediately call your gas supplier from a neighbor's phone. Follow the gas supplier's instructions.
8. If you do not smell gas go to next step.
9. Replace the upper access panel.
10. Turn on all electrical power to the unit.
11. Set the thermostat to desired setting.

ℹ️ NOTE - When unit is initially started, steps 1 through 11 may need to be repeated to purge air from gas line.

If the appliance will not operate, follow the instructions "Turning Off Gas to the Unit" and call your service technician or gas supplier.

Turning Off Gas to the Unit

⚠️ WARNING

If overheating occurs or if gas supply fails to shut off, shut off the manual gas valve to the appliance before shutting off electrical supply.

1. Set the thermostat to the lowest setting.
2. Turn off all electrical power to the unit if service is to be performed.
3. Remove the upper access panel.
4. Move switch on gas valve to OFF. Do not force. See figure 3.
5. Replace the access panel.

Thermostat Setting Warning

⚠️ WARNING

Do not set thermostat below 60°F (16°C) in heating mode. Setting thermostat below 60°F (16°C) reduces the number of heating cycles. Damage to the unit may occur that is not covered by the warranty.

Filters

All SL280UHNVK filters are installed external to the unit. Filters should be inspected monthly. Clean or replace the filter(s) when necessary to ensure proper furnace operation. A filter must be in place when the unit is operating. See table 1 for recommended filter sizes.

ℹ️ NOTE - Use replacement filters that are similar in size and efficiency ratings to those originally provided by the installing contractor. Use of replacement filters with higher filtration ratings may restrict air flow to the furnace. This may result in reduced unit efficiency, as well as premature blower motor failure.

Table 1: Recommended Filter Sizes

Maintenance

⚠️ CAUTION

As with any mechanical equipment, contact with sharp sheet metal edges can result in personal injury. Take care while handling this equipment and wear gloves and protective clothing.

A licensed professional service technician (or equivalent) should inspect the complete system each season (heating and cooling). The following maintenance procedures should only be conducted by a licensed professional service technician (or equivalent).

Do not attempt to service the unit in any way.

⚠️ WARNING

ELECTRICAL SHOCK, FIRE, OR EXPLOSION HAZARD. Failure to follow safety warnings exactly could result in dangerous operation, serious injury, death or property damage. Improper servicing could result in dangerous operation, serious injury, death, or property damage.

Before servicing, disconnect all electrical power to furnace. When servicing controls, label all wires prior to disconnecting. Take care to reconnect wires correctly. Verify proper operation after servicing.

⚠️ CAUTION

To ensure proper operation, a licensed professional service technician (or equivalent) should check the burner flame and conduct a combustion analysis annually.

Annually (before heating season) inspect furnace venting system, vent cap, heat exchanger and burners for corrosion, deterioration, or deposits of debris. Remove any obstructions.

Inspect the furnace venting system to make sure it is in place, physically sound and without holes, corrosion, or blockage. The vent connector must be correctly positioned and sloped upward. The vent connector must be physically sound, without holes or excessive corrosion.

Inspect the furnace return air duct connection. The duct must be sealed to the furnace and it must terminate outside the space containing the furnace.

Inspect the physical support of the furnace to guarantee that it is sound. The support must not sag and must not have cracks or gaps around the base of the furnace. There must be a seal between the furnace base and the support.

During a seasonal check, the service technician will inspect the indoor blower and the burner flames along with the venting system.

Blower

Check blower wheel for any debris and clean it, if necessary. The blower motor is pre-lubricated for extended bearing life. No further lubrication is needed.

⚠️ WARNING

The blower door must be securely in place when the blower and burners are operating. Gas fumes, which could contain carbon monoxide, can be drawn into the living space resulting in personal injury or death.

Service Reminder

Call your Lennox service technician if the unit will not operate. Before calling, always check the following to be sure service is required.

1. Check that electrical disconnect switches are ON.
2. Check room thermostat for proper setting.
3. Replace any blown fuses or reset circuit breakers.
4. Gas valve should be ON.
5. Air filter should not be plugged, which will limit air flow.
6. Is gas turned on at meter?
7. Is manual main shut-off valve open?

Record the model and serial number of the furnace. These numbers are on the unit nameplate, which is located below the burners.

Serial Number ________________________________

Model Number ________________________________

Safety Precautions

If you discover any of the following, shut down your unit, and contact a Lennox dealer for an inspection by a licensed professional service technician (or equivalent).

• If you repeatedly hear any new or unfamiliar sounds while your unit is operating, there may be a problem. For example, poorly performing burners can produce unfamiliar noises.
• If you smell any unusual odors, your unit may be operating improperly. For example, units can give off unfamiliar odors if components are required to operate in abnormal conditions.
• Look for visible signs of a malfunctioning unit. Examples include unusual amounts of condensate on windows inside your house, visibly burnt components or unusual dirt or rust accumulations on the vent pipe or in the unit.
• If you experience headache, nausea, fatigue, or dizziness, the cause could be exposure to carbon monoxide gas. This is often misdiagnosed as the flu because symptoms are similar. If you suffer from flu-like symptoms that are exaggerated at home, but seem to subside while you are away from the house, exposure to carbon monoxide could be the cause.
• If the indoor blower is running continuously at the cooling speed when thermostat is not calling for cooling demand you may have a refrigerant leak.

Your vigilance may pay off in early detection of a problem before either personal injury or property damage occurs. Do not hesitate to contact a qualified service technician as an investment in your well being.

⚠️ WARNING

Do not use this furnace if any part has been underwater. A flood-damaged furnace is extremely dangerous. Attempts to use the furnace can result in fire or explosion. Immediately call a licensed professional service technician (or equivalent) to inspect the furnace and to replace all gas controls, control system parts, and electrical parts that have been wet or to replace the furnace, if deemed necessary.

Planned Service

Annual Furnace Maintenance

At the beginning of each heating season, and to comply with the Lennox Limited Warranty, your system should be checked as follows by a licensed professional service technician (or equivalent).

1. Check wiring for loose connections, voltage at indoor unit and amperage of indoor motor.
2. Check the condition of the belt and shaft bearings if applicable.
3. Inspect all gas pipe and connections for leaks.
4. Inspect thermostat wires and refrigerant sensors for damage.
5. Check the cleanliness of filters and change if necessary (monthly).
6. Check the condition and cleanliness of burners and heat exchanger and clean if necessary.
7. Check the cleanliness of blower assembly and clean the housing, blower wheel and blower motor if necessary.
8. Inspect the combustion air inducer and clean if necessary.
9. Evaluate the heat exchanger integrity by inspecting the heat exchanger per the AHRI heat exchanger inspection procedure. This procedure can be viewed at www.ahrinet.org.
10. Ensure sufficient combustion air is available to the furnace. Fresh air grilles and louvers (on the unit and in the room where the furnace is installed) must be properly sized, open and unobstructed to provide combustion air.
11. Inspect the furnace venting system to make sure it is in place, structurally sound, and without holes, corrosion or blockage. Vent system must be free and clear of obstructions and must slope upward away from the furnace. Vent system should be installed per the National Fuel Gas Code.
12. Inspect the furnace return air duct connection to ensure the duct is sealed to the furnace. Check for air leaks on supply and return ducts and seal where necessary.
13. Check the condition of the furnace cabinet insulation and repair if necessary.
14. Perform a complete combustion analysis during the furnace inspection to ensure proper combustion and operation. Consult Service Literature for proper combustion values.
15. Verify operation of CO detectors and replace batteries as required.
16. The refrigerant leak detection sensor must be inspected for dust/debris deposits. Please refer to the evaporator coil and/or refrigerant detection sensor kit instructions for additional information.

Perform a general system test. Turn on the furnace to check operating functions such as the start-up and shut-off operation.

1. Check the operation of the ignition system, inspect and clean flame sensor. Check microamps before and after. Check controls and safety devices (gas valve, flame sensor, temperature limits). Consult Service Manual for proper operating range. Thermal Limits should be checked by restricting airflow and not disconnecting the indoor blower. For additional details, please see Service and Application Note H049.
2. Verify that system total static pressure and airflow settings are within specific operating parameters.
3. Clock gas meter to ensure that the unit is operating at the specified firing rate. Check the supply pressure. Do not check manifold pressure. Manifold pressure is NOT adjustable.
4. Low GWP (A2L) mitigation capability must be tested per the Low GWP test button functionality section in the furnace installation instructions.

Repair Parts

The following repair parts are available through Lennox dealers. When ordering parts, include the complete furnace model number listed on the CSA International nameplate -- Example: SL280UH060NV36AK-0. All service must be done by a licensed professional installer (or equivalent), a service agency, or the gas supplier.

Cabinet Parts

• Upper access panel
• Blower access panel
• Top Cap

Control Panel Parts

• Transformer
• Ignition control
• Door interlock switch
• Circuit breaker

Blower Parts

• Blower wheel
• Motor
• Blower housing cut-off plate

Heating Parts

• Flame Sensor
• Heat Exchanger Assembly
• Gas Manifold
• Combustion Air Inducer
• Gas Valve
• Main Burner
• Main Burner Orifice
• Pressure Switch
• Ignitor
• Primary Limit Control
• Thermal Switch

Refrigerant Detection System Parts

• Refrigerant detection sensor
• Refrigerant line set sleeve